Added options, suppressions and re-implemented BackendVFS::AsyncLockfreeFetcher to try and make valgrind happy.

This will remove contention on the drive register as drives uipdate their statuses.
Also simplified structures in OStoreDB implementation (less references with added friend relations).

The updating of statistic in the objecttore (in drive register) could wait for a lock
for so long that the session get killed due to a heatbeat timeout.

To avoid this, we use lockfree access as much as possible, and when locking it srequired, do it with a
timeout.

The timeout will be logged as a warning.

Added timeouts to synchronous locking primitives in the object store backends to implement this feature.

Fixed a bug where the VFS backend always used exclusive locks.

Work in progree: Changed layout of GenericObject::asyncLockfreeFetch so it matches the model of previous sync operations

like ArchiveRequest::asyncUpdateJobOwner().
Also made the no lock management match the model of previously developped nolock operations.
Removed Backend::AsyncLockfreeFetcher::wait() as get() will pass the exceptions anyway.

the Backend.

Proceed all successful reports asynchronously and periodically check
and clear statuses if they have finished.
In the end of session do the check/flush for all reports in the
successful reports queue.

Switch from synchronous rados remove to async aio_remove in
case of zero size object in BackendRados::AsyncUpdater

Added an intermediate interface to reuse SchedulerDatabaseFactory.
Added optional debug infos for BackendVFS constructor.
The unit test is currently disabled.

The VFS implementation only launches the operation in the background (via std::async).
The Rados implementation uses the aio features of Rados. Lock and update are launched in the background via std::async.
Also now uses override for Backend virtual function.

Added a list method for the backends so we can clean up the rados store before running each unit test, which expects a fresh store.
Added a new command line tool to list the contents of the backends.

New URLs are rados://user@pool and file:///tmp/XXXXX. Otherwise, we fall back to interpreting
the URL as a bare path.

License comment is no longer filtered out by doxygen when generating web pages of the individual source files.

Implemented the new interface on the Rados backend.
Fixed several bugs.

The context handle concept is being dropped, with scoped lock objects in place.
The VFS backent store now compiles.